I fully second the comments in the previous post. Steve, going thru this thread makes me pretty confident that you are one of the best out there, technically as well as professionally. You are providing your expertise free of charge on this forum, and that is something that we all truly appreciate. And as has been said earlier, man if I was within a few hundred miles of your shop, I would never go to any other mechanic.
But the unfortunate reality is that in my 11 years of experience in maintaining a mercedes, unfortunately, 75% of the shops/mechanics I have come across have been either incompetent, or unscrupulous, or both. And this is when 50% of them have been at authorized mercedes dealers, in 3 different cities. I can give you tons of examples of authorized dealer technicians giving WRONG advice, just to make money. To top it off, more often they have not had a clue as to what the problem was. This problem is exacerbated by the individual called "service advisor" at these dealers. He is probably a used car salesman, who behaves like a salesman, not like a tech, had zero knowledge, and will say any crap just to make money. I guess that's his job. And he is the one you have to deal with, or through. You won't believe the kind of quotes I have obtained, and the unnecessary repairs that have been suggested, or the "diagnostic" charges that have been levied without any result. I had a rough idle at cold, and 1500 dollars later, it was solved when the oxygen sensor was found totally dead. Shouldn't the tech have noticed it the first time he tried to adjust the fuel mixture - the output was constant. and I can go on and on. Believe me, since you are a tech, you probably haven't experienced the frustration of a person who doesn't know too much about cars, being taken for a ride again and again and again, by people who you would think one could trust - the authorized dealers and independent MB specialist. There is only one, I repeat, one one guy I found to be both honest and competent (he is in Queens, NY). Anyone else I went to, first asked me to shell out at least a grand.
So that's the reality out there. Again, Steve, its all the more commendable, and a relief, to see people like you around. Maybe you should branch out, set up shops all over the country, and get these bad guys out of business. I will personally make sure everyone I know comes to you for repairs.